fix #7037

Author: NikolajBjorner

Diff for: src/smt/theory_datatype.cpp

@@ -509,10 +509,10 @@ namespace smt {
     // Assuming `app` is equal to a constructor term, return the constructor enode
     inline enode * theory_datatype::oc_get_cstor(enode * app) {
         theory_var v = app->get_root()->get_th_var(get_id());
-        SASSERT(v != null_theory_var);
+        if (v == null_theory_var)
+            return nullptr;
         v = m_find.find(v);
         var_data * d = m_var_data[v];
-        SASSERT(d->m_constructor);
         return d->m_constructor;
     }
 
@@ -802,8 +802,9 @@ namespace smt {
             return false;
         func_decl* con = m_util.get_accessor_constructor(f);
         for (enode* app : ctx.enodes_of(f)) {
-            enode* arg = app->get_arg(0)->get_root();
-            if (is_constructor(arg) && arg->get_decl() != con) 
+            enode* arg = app->get_arg(0);
+            enode* arg_con = oc_get_cstor(arg);
+            if (arg_con && is_constructor(arg_con) && arg_con->get_decl() != con) 
                 return true;
         }
         return false;